Sterilization methods are used in a broad range of applications, and have used an equally broad range of sterilization agents. As used herein the tern “sterilization” refers to the inactivation of all bio-contamination, especially on inanimate objects. The term “disinfectant” refers to the inactivation of organisms considered pathogenic.
Gaseous and vapor sterilization/decontamination systems rely on maintaining certain process parameters in order to achieve a target sterility or decontamination assurance level. For hydrogen peroxide vapor sterilization/decontamination systems, those parameters include the concentration of the hydrogen peroxide vapor, the degree of saturation, the temperature and pressure and the exposure time. By controlling these parameters, the desired sterility assurance levels can be successfully obtained while avoiding condensation of the hydrogen peroxide due to vapor saturation.
Conventional Vaporized Hydrogen Peroxide (VHP) sterilization systems for decontaminating large rooms or isolators are generally closed-loop systems that contain a destroyer and a dryer within the system. In such system, a sterilant is continuously conveyed through the room or isolator. Sterilant exiting the isolator or room is directed to the destroyer to break down the vaporized hydrogen peroxide into water and oxygen. This type of arrangement allows the vaporized hydrogen peroxide concentration within the system to be maintained at a desired concentration depending on the airflow and sterilant (normally 35% hydrogen peroxide, 65% water by weight in a liquid state).
During a decontamination cycle, the room or isolator to be decontaminated is first dried to a low humidity level using a desiccant dryer. After the drying phase is complete, a conditioning phase is run wherein sterilant is injected into the room or isolator at a relatively high rate to bring the hydrogen peroxide level up to a desired concentration level in a short period of time. After the conditioning phase, the decontamination phase is run where sterilant injection rate is decreased to maintain the hydrogen peroxide level at a constant concentration level. After the decontamination phase, the enclosure is aerated by turning off the sterilant injection. Aeration is run until the hydrogen peroxide level is below an allowable threshold (usually 1 ppm).
A problem with such systems, particularly during a conditioning phase, is that because the destroyer and dryer are part of the closed loop system, the vaporized hydrogen peroxide is destroyed as it exits the room or isolator to be decontaminated. As a result, the vaporizer must continuously introduce new sterilant into the air stream entering the room or isolator. This method of operation limits the rate at which the concentration of sterilant can be increased into the isolator or room during a conditioning phase. For smaller enclosures, the conditioning phase does not greatly affect the overall cycle time. However, for large rooms or isolators, i.e., areas of 5,000 ft3 or larger, this can greatly affect the condition time.
The present invention overcomes this and other problems, and provides a decontamination system that increases the rate at which the concentration of a sterilant can be increased within a room or isolator.